Association between Osteoporosis, Bone Mineral Density Levels and Alzheimer's Disease: A Systematic Review and Meta-analysis

We aimed to perform a systematic literature research and meta-analysis to explore the association between osteoporosis/bone mineral density (BMD) and Alzheimer's disease (AD). PubMed, Embase, and Web of Science were searched up to 31 December 2016, and the reference lists of relevant articles were also checked. Association between osteoporosis and AD was qualitatively analyzed, and BMD with AD was analyzed using a meta-analysis. Pooled standardized mean difference (SMD) or hazard ratio (HR) and 95% confidence intervals (CIs) were calculated. The Q statistic and I2 methods were used to test for heterogeneity. We used subgroup analysis to explore possible sources of heterogeneity. Eight studies were included. Three provided data on osteoporosis and AD, and five reported BMD levels with AD. We performed two meta-analyses. The combined results indicated that AD patients had lower BMD compared with controls (SMD -1.23, 95% CI -1.93--0.54), and lower femoral neck BMD were associated with increased risk of AD after adjusting for confounding variables (HR 2.19, 95% CI 1.67--2.88), respectively. Our study suggested that AD patients are at higher risk for osteoporosis and have lower BMD than controls, while osteoporosis and lower femoral neck BMD are also associated with a higher risk of AD.